Pedro is an easygoing pit bull terrier who is Papi's adoptive brother, making him Chloe's brother-in-law and Papi Jr., Rosa, Lala, Pep and Ali's uncle. When Papi first introduces Pedro, the pit bull shows his teeth to Chloe and the puppies, who all become frightened because they think Pedro is vicious and wants to hurt them. Papi tries convincing them that Pedro isn't mean and that he was just smiling as his way of greeting guests. He and the others later find out that Sam and Rachel are losing their house. When Mr. Kroop and his employees come in, Pedro and the others begin to retaliate; however, the situation got worse as the eviction took effect faster.
Later on, Pedro, along with Papi, Chloe and Delgado, participate in a dog fashion show to win a large cash prize that would save Sam and Rachel's family home. Pedro becomes disqualified after he shows off his "smile" to the audience. Though Papi had initially won, because of the lack of breed papers, he is disqualified as well. Due to these actions, the dogs lose to an arrogant French poodle named Appoline, much to their chagrin.
Eager to help out, Papi and Chloe's kids venture out and find some bank robbers who had stolen a large sum of money. The puppies stow away in one of the bags, but are later found out by the robbers. Papi and Chloe soon discover their kids missing, and they, along with Pedro and Delgado, set out to look for them. Pedro finds a mask with the scent of bread on it, which leads them to the factory. The dogs locate the puppies, foil the robbery, and return home to find that they have been awarded more than enough money to save their house. Pedro and the dogs, along with their human owners, celebrate their victory and live happily ever after.
In Beverly Hills Chihuahua 3, Pedro comes along with the Chihuahua family to Langham. While lounging at the pool, he notices a beautiful dog named Charlotte with her owner and is smitten. However, his "smile" leaves her unimpressed and a little disgusted, much to his chagrin. He attempts to serenade her by singing; however, he messes up again. He and Papi accidentally wreck the gardens that Sam just perfected after Papi gets caught in some netting that Lester, Sam's lazy assistant, didn't pack up. Pedro and Papi later find out what Jenny and Oscar are actually up to and set a trap to catch them. When the deed is done, they throw Rosa's quinceanera, and Charlotte and Pedro finally become a couple. It is mentioned that sometime later, Pedro gains a VIP card and locks himself in the peanut butter closet.